//------------------------------------------------------------------------------
//  <copyright file="Interpolator.cs" company="Microsoft Corporation">
// The MIT License (MIT)
// 
// Copyright (c) 2014, Microsoft Corporation
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
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//------------------------------------------------------------------------------

namespace Microsoft.Robotics.Algorithms
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;

    /// <summary>
    /// Calculates a interpolated value
    /// </summary>    
    public static class Interpolator
    {
        /// <summary>
        /// Linear interpolate the given values to the desired timestamp.
        /// </summary>
        /// <param name="start">The start index for interpolation</param>
        /// <param name="end">The end index for interpolation</param>
        /// <param name="desired">Desired index for interpolation. This must be between (inclusive) start and end times</param>
        /// <param name="startValue">Start value</param>
        /// <param name="endValue">End value</param>        
        /// <returns>The linear interpolated value at the desired time</returns>
        public static double LinearInterpolate(long start, long end, long desired, double startValue, double endValue)
        {
            if (end <= start)
            {
                throw new ArgumentOutOfRangeException(string.Format("end time {0} should be greater than start time {1}", end, start));
            }

            if (start > desired || end < desired)
            {
                throw new System.ArgumentOutOfRangeException(string.Format(
                    "desiredTime {0} should be between startTime {1} and {2} inclusive",
                    desired,
                    start,
                    end));
            }

            // endtime >= starttime was already checked in constructor.
            double interpolationFactor = 1.0d * (desired - start) / (end - start);
            return startValue + (endValue - startValue) * interpolationFactor;
        }
    }
}
